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Purple Power

Beneficial: Caterpillar Parasites

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Beneficial: Caterpillar Parasites


(Trichogramma species)








Special Species Notes:



Caterpillar Parasites  Trichogramma is one of around 80 genera from the family Trichogrammatidae, controlling over 200 species of Caterpillars and moths. 30 species have been identified from North America and an estimated 20 to 30 species remain to be described. They are commonly used around the world. They have been the most extensively studied. Trichogramma are unique to the size limit of how small an insect can be, which would be determined by how few neurons they can fit in their central nervous system, yet exhibit a complex behavior to sustain their life. Trichogramma have less than 10,000 neurons, which is a hundred times fewer than the next smallest insect.


Wolbachia is a widespread bacterium that infects insect's organs, most commonly, the reproductive organs. Wolbachia has been observed to alter the host’s reproductive success upon infection. Through a series of manipulations, Wolbachia-infected hosts transmit this intracellular bacterium to uninfected individuals. These manipulations include male killing (increasing ratio of infected females who can reproduce), feminization (males become fertile females), parthenogenesis, and cytoplasmic incompatibility.  Causes infected females to asexually produce fertile females and nonfunctional males. Transmission of the bacterium through horizontal transfer has been observed within the same species and among different species of Trichogramma, including T. kaykai, T. deion, T. pretiosum, T. atopovirilia; however, there are limitations to transmission. In-vitro successful horizontal transfer is uncommon within Trichogramma, which suggests that the density of Wolbachia must be relatively high inside of the host’s ovaries. Commonly, uninfected wasps are unable to breed with infected wasps. Wolbachia can influence gender determination in its hosts so that more females are successfully born. This results in a reversal in sexual selection where females must compete for male mates, which has evolutionary implications as it exposes different phenotypes to natural selection.


Common species that are used are T. atopovirilia, T. brevicapillum, T. deion, T. exiguum, T. fuentesi, T. minutum, T. nubilale, T. platneri, T. pretiosum,  T. carverae, and T. thalense.


T. pretiosum is the most widely distributed Trichogramma species in North America. It was  introduced into Australia in the 1970s as part of the Ord River Irrigation Area (ORIA) IPM scheme.


T. carverae is used for biological control of light brown apple moth in vineyards. Though Australia has its own native Trichogramma species there has not been much work undertaken to commercially use them for biological control within Australia. The larvae are the stage that causes the most damage, especially to grape berries which provides sites for bunch rot to occur.




They're so tiny (1/50" from wingtip to wingtip, 0.2-1.5mm) and the size of a period at the end of a sentence. They are very uniform in structure which causes difficulty in identifying the separate species. 


females are all relatively similar whereas examination of males to tell the different species apart using features of their antennae and genitalia.



Life cycle:






Temperature:  68-81F;  can survive and reproduce at temperatures up to 104F


Humidity: over 60%


Total life span is 7-190 days, depending on temperature. Life cycle, eggs to adult,  takes 14 days at 70F. varies from 8 days when mid-summer temperatures are high (90 degrees F) to as many as 17 days at 60 degrees F. Adults are most active at 75 to 85 degrees F. There may be 30+ generations per season. Trichogramma overwinter as immature forms in host eggs. Some species enter a state of hibernation which allows them to tolerate long periods of subfreezing temperatures.


laying their eggs inside moth or butterfly eggs so that, instead of a new generation of Caterpillars, another Parasite generation hatches out and goes on to repeat the cycle. The male dies after mating. The mated female lays 60-70 eggs in the next week or 2.


A mated female tries to locate host eggs, She uses chemical and visual signals, such as egg shape and color. When she finds one, an experienced female will attempt to determine if the egg has previously been parasitized using her ovipositor and antennal drumming (tapping on the egg surface). Females also use antennal drumming to determine the size and quality of the target egg, which determines the number of eggs the female will insert. She can parasitize one to ten host eggs a day. A venom injected by the female at the time of oviposition is believed to cause this predigestion of the egg’s contents. Eggs hatch in about 24 hours and the parasite larvae eat and develop very quickly.


Larvae develop through three instars. During the 3rd instar (3 to 4 days after the host egg was parasitized) dark melanin granules are deposited on the inner surface of the egg chorion, causing the bollworm egg to turn black. Larvae then transform to the inactive pupal stage. After about 4 1/2 days, the adult wasps emerge from the pupae and escape the bollworm egg by chewing a circular hole in the egg shell.




What they eat and use as host:


They primarily use the offspring of various moths and butterflies and are controlled similarly.

Corn Earworm, Cabbage Looper, Tomato Hornworm, Cotton bollworm (Helicoverpa armigera), Codling moth (Cydia pomonella), budworms, Lightbrown apple moth (Epiphyas postvittana), European corn borer (Ostrinia nubilalis), army-worms (Spodoptera) and loop-ers (Trichoplusia).


Certain species of Trichogramma also parasitize eggs of beetles (Coleoptera), flies (Diptera), true bugs (Heteroptera), other wasps (Hymenoptera), and lacewings and their relatives (Neuroptera).






Most insecticides are very harmful to Trichogramma adults. However, the eggs, larvae, and pupae are afforded some protection from insecticides by the moth egg shell or the skin of its host in which they are enclosed.


Use the spray Bt, Bacillus thuringiensis against caterpillars rather than broad-spectrum insecticides - these kill your beneficials at rates higher than the target hosts. Although Bt will kill most larvae, it doesn't harm wasp pupae or adults. It was found to be harmless to all the development stages of the tested Trichogramma species. slightly harmful only to T. bourarachae prepupae stage The percentage of partial emergence from eggs exposed to B. thuringiensis was similar to that of the control. The day after insecticide treatment; B. thuringiensis actions on all studied Trichogramma species were comparable with those of the control, whereas deltamethrin and spinosad continued to be harmful to adults during the first, the second and even the sixth day after insecticide pulverisation.


In studies, parasitized eggs that were exposed to spinosad displayed the highest mortality rate during adult emergence, followed by eggs exposed to deltamethrin However, T. evanescens and T. bourarachae larvae stages were among the most touched by mortality during adult emergence, whereas for T. cacoeciae, this phenomenon was higher for prepuae stages than for larvae and pupae stages, when treated with spinosad.



Beneficial Plants: How to Attract and Keep Them


Provide them a diversity of plants with single blossomed flowers and flowering herbs since they consume nectar and pollen. This will help welcome them to your garden. Choose: allium, alyssum, cosmos, dill, fennel, lemon balm, thyme, statice, Fern-leaf yarrow and zinnia, Queen Anne's lace, cole crops, Common yarrow, Lavender globe lily, dill, Golden marguerite, Masterwort, Purple poppy mallow, Caraway, Coriander, Cosmos white sensation, Fennel, Statice, Butter and eggs, Edging lobelia, Sweet alyssum - white, Lemon balm, Pennyroyal, Parsley, Sulfur cinquefoil,, Alpine cinquefoil, Orange stonecrop, Marigold - lemon gem, Tansy, Crimson thyme, Zinnia - liliput.






If outdoors, release during the morning. Keep Trichogramma in the shade, out of the hot sun. Emergence can be delayed by holding parasitized moth eggs at cooler temperatures (not less than 40º F).


Caterpillar Parasites come as eggs ready to hatch. 5,000 eggs glued to a small piece of cardboard. Placed around the garden, they'll hatch and breed from there.


Parasites should be released when Pest Moths or Caterpillars are first seen, and further releases continued weekly or bi-weekly until Caterpillars are no longer present. Use 5,000 - 25,000 per acre, depending on the level of infestation.


Loose parasitized eggs can be incubated in a variety of containers (preferably glass or paper over plastic). Jars or vials, bags or cups can be used. Loose eggs are divided into roughly equal amounts among containers. Large containers can be opened at randomly spaced rows or trees releasing more where moth activity has been greater.


Emerging wasps are usually seen in the morning, first males sitting quietly, then females and mating activity, then the males die.






The link below will take you to "An Intro to beneficial bugs and beneficial insect food" it has a list (been worked on) to pests and beneficial insects









Classy, sassy, and a bit of a smart assy

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Caterpillar Parasites are beneficial for the environment through the collective relationship they maintain with the plants they visit.  But sometimes caterpillars are harmful to plants they eat your garden plants. When controlling a caterpillar is required, hand-picking is among the most effective solutions. Another method of controlling them is using insecticide sprays or powder. Using of insecticide you need to use it with proper amount, so hire or consult some exterminator in Long Island who will use an effective commercially available spray for caterpillars.

Edited by MarianGuzman

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